The invention relates to a windshield wiper system with two opposite wipers and two synchronized reversing motors wherein the wipers overlap at least partially with their wiper blades in a parked position and wherein each reversing motor is driven via an associated lever mechanism of a wiper.
This type of wiper system is known from DE 103 06 496 A1, for example.
Different wiper field types and drive devices are known in order to clean windshields of motor vehicles. In the case of wiper fields, a differentiation is made mainly between single-lever wiper fields and dual-lever wiper fields. In the case of the dual-lever wiper fields, the wiper levers comprised of a wiper arm and a wiper blade can be driven in the same direction or in the opposite direction.
As a rule, till now the drive device has only one wiper motor even for two windshield wipers and the rotating drive movement of its output shaft is translated via a crank mechanism into an oscillating rotating movement of the drive shafts of the windshield wipers. Newer wiper motors are equipped with electronics, which regulate a reversing drive movement of the output shaft. In addition, the electronics make possible wiping angle control with a dynamic, load-dependent wiping angle correction and wiper speed regulation. In addition, the electronics permit various wiper functions and positions, i.e., an expanded parking position.
Wiper systems with opposite windshield wipers are frequently used to wipe large windshields. If these are driven by one wiper motor, the result is a great need for construction space in the center of the vehicle along with a large construction size corresponding to the vehicle width. Besides this, the kinematic structure with or without intermediate bearings is expensive and requires a large, powerful wiper motor. The many individual mechanical components give rise to large static wiping angle tolerances, to which dynamic wiping angle tolerances are added, which are caused by the elasticities of the mechanical components as well as the supporting and fastening elements.
In order to achieve a simpler kinematic structure and thereby lower wiping angle tolerances, wiper systems with two wiper motors are used, which are arranged in the area of the wiper bearings and therefore do not occupy any construction space in the center area of the windshield. Two synchronized wiper motors with electrical communication are used to drive the wipers. The two wiper motors are preferably regulated by control electronics in reversing operation in order to achieve the advantages associated therewith. In the process, when the wiper has reached the upper reversal position on the window, a reversing signal to reverse the direction of rotation is generated by the electronics and is fed to the respective motor. As for the rest, the wiper drive, as described in DE 100 45 573 A1 for example, is comprised of a motor crank placed on the output shaft of the respective motor, and the motor crank drives a rocker arm in a pendulum fashion via a lever mechanism, which rocker arm is in turn suitable for driving a wiper arm or a wiper arm linkage. This arrangement is used for rotary and reversing motors, wherein the lever mechanism must be adapted to the drive type.
In actuality, dual-motor opposite-direction wiper systems are being used more and more frequently in vehicles with opposite-direction wiper systems because of installation conditions and motor torque requirements. In the case of these opposite-direction wiper systems, because of the overlapping arrangement of the wiper levers, the wiper levers can collide and get blocked on the vehicle when the wiping movements of the two wiper levers deviate from the target movement. The deviations of the control curves of the wiping movements from the theoretical target curve are caused by mechanical manufacturing tolerances and regulator deviations of the electrically controlled wiper system drive modules. Even with ideally synchronized motor output shafts, deviations, which express themselves as randomly distributed mechanical phase displacements between the wiping movements of the wipers, can occur because of the downstream mechanics.
If the total of the phase displacements of the wiping movements between the driver's side and passenger side modules of a dual-motor wiper system turn out to be unfavorable, this produces a collision when there is an insufficient minimum distance between the wiper levers. However, the greater safety distance of the wiper blades from one another that is required because of the tolerance-encumbered control curves goes hand in hand with the disadvantage of less harmonic wiper operation.
The object of the invention is designing a windshield wiper system of the type cited at the outset in such a way that the risk of collision of the wipers that is caused by the manufacturing and electronic tolerances can be reduced without having to increase the safety distance of the wiper lovers.